Tooth positioner with harder areas

ABSTRACT

Tooth positioner comprising several integral tooth engaging portions formed of materials having different hardness, the harder portions of which assist in anchoring the tooth positioner in its proper position in the patient&#39;s mouth. 
     Further, a method of making such tooth positioners by enclosing dental counterpart of the mold to form a first portion of the positioner, placing at least one other material into the mold in interfacing relation to the first portion to form a second portion of the tooth positioner, and curing the several materials into an integral body before extracting the positioner from the mold.

TECHNICAL FIELD

The present invention is an improved appliance primarily for use inorthodontic procedures, known as a tooth positioner, and a method formanufacturing improved tooth positioners.

BACKGROUND ART

Tooth positioners are well known orthodontic appliances formed as anarch shaped body of resilient material fitting within a patient's mouthbetween the upper and lower arches. Tooth positioners have a generallyconcave surface for bearing on the buccal and labial surfaces of theteeth of at least one arch and a convex surface adjacent to the lingualsurface of the patient's teeth. Tooth positioners for moving teeth intoa more desired configuration are made by taking a cast of the upper andlower arches, moving teeth in the cast counterpart to more preferredpositions, packing or pouring uncured material around the counterpart,curing this material to form a resilient arch shaped body, and trimmingthe outer surfaces of the body as necessary to make a finishedappliance. Such tooth positioners are described, for example, in U.S.Pat. Nos. 2,467,432 and 2,531,222.

Such tooth positioners can be difficult to secure in the proper positionin the patient's mouth, particularly when the tooth impressions in thepositioner have been moved with respect to the existing positions of thepatient's teeth. Deformation of such an appliance to fit it in thepatient's mouth frequently creates stresses which tend to unseat ordisplace part of the tooth positioner from its proper position, thuslimiting its therapeutic value. In prior art tooth positioners thisseating problem has been addressed by providing protruding metal clipsor hooks in the positioner to engage the patient's teeth. If properlyanchored, such clips or hooks can assist in seating the positioner, butconcentrate the force in very small areas. In some patients they maydamage teeth or cause pain when the positioner is worn particularly ifthey terminate at or near the gum line. In another approach, taught inU.S. Pat. No. 4,055,895 (issued to Huge to Nov. 1, 1977), prestressedelastic bands are incorporated in the tooth positioner so that inwardpressure, which can assist in seating the tooth positioner, is exertedon all the teeth of one or both arches. But in certain circumstancesprestressed bands in the tooth positioner do not completely solve theseating problem.

Such tooth positioners also must have minimal bulk and weight,especially in the bite portions, to provide a correct andcomfortable--or "anatomical"--fit. Yet, the positioners must be durableto resist bite-through and must have sufficient tensile strength andelasticity to move the patient's teeth to the desired positions.Previous positioners have not reached these goals, or have reached oneat the expense of another.

Finally, tooth positioners have been made having two or more integrallyformed portions of different hardness; one example of such a device is atooth positioner made with relatively soft tooth engaging portions and ahard shell-like front to stiffen the appliance and to enable it toprotect the patient's teeth while the device is worn. The harder part ofthe appliance does not engage the patient's teeth to assist in anchoringit in place.

SUMMARY OF THE INVENTION

The present invention is an improved tooth positioner comprising firstand second integrally formed portions, one of which is harder than theother, engaging the patient's teeth. The harder and softer portions ofthe appliance can be variously arranged, so long as each portion engagesat least one tooth in the patient's mouth. The harder portions can, forexample, comprise a reduced bite portion or flange portion of thepositioner to allow construction of an anatomical positioner which stillresists bite-through and has adequate tensile strength. The harderportions can also anchor the positioner in place by engaging certain ofthe patient's teeth. The harder portion is that part of thetooth-engaging sockets that engage those teeth of the patient which areto serve as anchors and remain unmoved while the positions of otherteeth are corrected primarily by engagement with the softer portions.Generally the molar teeth will be the anchors. The harder materialshould be Shore A Durometer 75 to 90, and the softer material 60 to 80Shore, with a substantial difference between them. Wherever Shorehardness is referred to herein, Shore A hardness scale for elastomers isreferred to.

My invention further includes the method of producing such articles byplacing corrected tooth models in a container or flask, pouring one ofthe materials, allowing partial setting, pouring the other material, andcuring to an integral resilient two-hardness body.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top perspective view of an improved tooth positioner.

FIG. 2 is a top plan view of the tooth positioner shown in FIG. 1.

FIG. 3 is a top plan view of an alternate tooth positioner.

FIG. 4 is a top plan view of another alternate tooth positioner.

FIG. 5 is a front elevation of still another alternate tooth positioner.

FIG. 6 is a cross section taken along line 6--6 in FIG. 1.

FIG. 7 is a cross section taken parallel to the occlusal plane of amolding flask and counterpart for making tooth positioners according tothe present invention.

FIG. 8 is a cross section in the saggital plane of an alternate moldingflask and counterpart.

DESCRIPTION OF PREFERRED EMBODIMENTS

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structure. While the best known embodiment has beendescribed, the details may be changed without departing from theinvention, which is defined by the claims.

The tooth positioner 20 shown in FIGS. 1 and 2 is an arch shaped body ofresilient material formed to fit within a patient's mouth between theupper and lower arches of teeth. Positioner 20 defines impressions suchas 21 of the patient's teeth in their preferred positions in thepatient's mouth. The lingual surfaces of the tooth impressions defineconvex flanges 23 adjacent the lingual surfaces of the teeth, while thebuccal and labial surfaces of the tooth impressions define generallyconcave flanges 23 for bearing on the buccal and labial surfaces of theteeth of at least one arch. Referring briefly to FIG. 6, surfaces 22 and23 are joined by a bite portion 24 which lies in the occlusal plane andreceives the cutting surfaces of a patient's teeth when the positioneris worn. Portions of the bite portion and/or flanges can be formed ofharder material having higher tensile strength and greater resistance tobite-through than the other parts of the positioner, as taughthereinafter, allowing their dimensions to be reduced. An anatomicalpositioner can thus be formed without compromising its strength ordurability.

Returning to FIG. 1, one such structure having portions of differinghardness is shown. The tooth positioner has a proximal portion 25 whichseparates distal portions 26 and 28 made of different material thanproximal portion 25, and the three portions of the tooth positioner arejoined at interfaces 30 and 32 which lie in roughly vertical planes whenthe appliance is worn. Portions 25, 26, and 28 each are integral partsof the positioner, and each engages at least one tooth.

In one embodiment of the present invention the distal portions 26 and 28of the positioner are formed from relatively harder resilient materialto provide an anchor, while proximal portion 25 is formed of softermaterial. In an alternate embodiment of the invention the harder andsofter materials may be exchanged. In either case the harder materialcan have a Shore A Durometer hardness of from about 75 to about 90, andthe softer portion can have a Shore A Durometer hardness of from about60 to about 80. In a preferred embodiment of the invention the harderportion is about 10 units harder than the softer portion of the Shore ADurometer scale. Materials harder or softer than those in the foregoingranges can also be used. Also, appliances can have three or moreportions having different hardnesses without departing from the scope ofthe present invention.

In tooth positioner 34 shown in FIG. 3 one distal end, 28, is joined toa second portion encompassing the proximal and distal portions 24 and 26of the positioner, at interface 32. Again, either portion of positioner34 can be harder than the other portion.

FIG. 4 shows another alternate embodiment 36 of the invention in whichthe interfaces 30 and 32 dividing the respective portions of thepositioner 36 lie in generally vertical planes which are roughlyperpendicular to the planes of the interfaces shown in FIGS. 2 and 3.FIG. 4 also illustrates that one or both distal portions of theappliance can vary in length.

FIG. 5 shows another alternate tooth positioner 38 having a lowerportion 40 made of material having a different hardness than upperportion 42; the lower and upper portions are divided by interface 44which in this embodiment is in the occlusal plane when the appliance isworn. Either portion may be harder than the other.

Although the tooth positioners of FIGS. 1 through 5 do not show anyseating adaptations other than differential hardness, other seatingdevices, such as conventional clips or wires, integral or externalresilient bands, rigid sockets, or the like may be included in the toothpositioner.

Each portion of the tooth positioner can be formed by pouring a liquidmaterial into the mold flask 46 (FIGS. 7 and 8) containing a counterpart47 when the mold is so oriented that the flat upper surface of thepoured material is formed at the site of the intended interface with thenext layer to be poured. Flask 46 is modified to the extent of making itfluid tight and providing sprues 48, 50, 52, 54, 56, 58, or 60, or anyof them, to allow liquid materials to be poured or injected into themold. Thus, if a tooth positioner as shown in FIGS. 1 and 2 is to beformed, the mold can be oriented so that the proximal teeth 64 of thecounterpart are in the lowest part of the mold (as shown in FIG. 8).Next, the material to form the proximal portion 25 of the positioner ispoured into the mold. Then the material to form the distal portions 26and 28 is poured into the mold. After the respective portions of thepositioner are poured, the positioner can be cured to a form retainingstate. The mold and positioner are then separated to release the finaltooth positioner. The positioner can be machined to provide outersurfaces having a pleasing and professional appearance.

To form the tooth positioners shown in FIGS. 4 and 5 from liquid rawmaterials the previously described procedure is used, but the mold isoriented differently while the respective materials are poured into itin order to provide interfaces in the finished product which havedifferent orientations than those shown if FIGS. 1, 2, and 3. To formthe structure shown in FIG. 4, the mold shown in FIG. 8 is rotated aquarter turn in the occlusal plane so that one distal end of thecounterpart is above the other distal end and the arches are in avertical plane. Access to the mold interior is provided by sprues at theupper distal end of the counterpart so that the first material can bepoured into the counterpart. When the first material is poured into themold, it flows into the lowermost distal end and forms a flat surface atthe position of interface 32 as shown in FIG. 4. The material of theproximal portion of positioner is then poured into place. At least thejust poured proximal portion of positioner is then cured sufficiently toretain its form, the mold is returned to the orientation shown in FIG.8, and the other portion of the tooth positioner is cast.

The tooth positioner shown in FIG. 5 can be cast from liquid rawmaterials by orienting the assembled mold with its occlusal planehorizontal.

In an alternate method of forming the tooth positioners of the presentinvention, granular or bulk uncured solid materials (such asunvulcanized rubber) can be assembled in a mold flask in the desiredpositions and cured, fusing the several materials together to form anintegral appliance. The compositions of the uncured compositions arevaried so the same curing conditions yield regions of differinghardness. This method can be practiced using the well-known mold flasksfor forming vulcanized tooth positioners.

The materials of the respective portions of the tooth positioner must becarefully selected to be compatible so that they will join to form anintegral product, but one portion must not be allowed to diffuse sosubstantially into the next that the final appliance does not haveseparate portions of distinctly different hardness. If liquid rawmaterials are used, the necessary separation of materials can beaccomplished by providing a second liquid material with a specificgravity no greater than that of the first liquid material, so gravitywill not tend to mix the two liquid materials. Alternatively, the firstliquid material poured into the mold can be partially or completelycured to harden it into a form retaining state before a subsequentmaterial is poured into the mold. Thus, the material can be added as aliquid and readily conform itself to the mold surfaces, but it will actas a solid material when the next material is poured. Finally, if thematerials have sufficiently high viscosities or are not liquids, theymay not mix at a high enough rate to cause a problem.

One can also form a tooth positioner according to the present inventionusing incompatible adjacent materials if a thin adhesive layer which iscompatible with both materials is inserted at the interface to bond thefirst and second incompatible materials together.

The materials used to form the tooth positioner are each formulated tocure to a specific hardness so that different portions of differenthardness can be formed under the same molding conditions. Alternatively,a first portion can be placed in the mold and cured to provide a hardmaterial, and subsequent material added to the mold can be cured underconditions which yield a softer cured mass, thus providing differenthardnesses in the several portions of the tooth positioner.

The various tooth positioner configurations shown in the presentdisclosure are merely representative, as other configurations can bereadily prepared by one skilled in the art of forming tooth positioners.

I claim:
 1. In tooth positioner means comprising an arch-shaped body ofresilient material having an integrally formed tooth engaging proximalregion and first and second integrally formed tooth engaging distalregions, said tooth positioner means being formed to fit within apatient's mouth between the upper and lower arches, such means having agenerally concave surface for bearing on the buccal and labial surfacesof the teeth of at least one arch and having a convex surface adjacentto the lingual surface of the teeth, the improvement wherein at leastone of said proximal and distal regions of said arch-shaped body is ananchoring region composed of harder material than another of saidproximal and distal regions.
 2. The tooth positioner of claim 1, whereinat least one of said distal regions is composed of harder material thansaid proximal region.
 3. The tooth positioner of claim 2, wherein eachof said distal regions is composed of harder material than said proximalregion.
 4. The tooth positioner of claim 1, wherein said proximal regionis composed of harder material than at least one of said distal regions.5. The tooth positioner of claim 4, wherein said proximal region iscomposed of harder material than each of said distal regions.
 6. Thetooth positioner of claims 1, 2, 3, 4, or 5, wherein each harder regionhas a Shore Durometer hardness of from about 75 to about 90, and whereinat least one other region has a Shore Durometer hardness of from about60 to about
 80. 7. The tooth positioner of claim 6, wherein said harderregion is about 10 Shore Durometer hardness units harder than at leastone other of said distal and proximal regions.